• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.199-202
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• 2004

In this present study, an attempt was made to determine the deformation mode of the Zr-Ti-Cu-Ni-Be bulk metallic glass by compression test over a wide range of temperatures and strain rates. From the results, empirical deformation map could be constructed including the boundaries of different deformation modes. Considering power dissipation map and instability map developed on the basis of the Dynamic Materials Model (DMM), the processing map for extrusion could also be constructed. In addition, the macroscopic formability of this BMG alloy has also been examined through the extrusion in laboratory scale within undercooled liquid state. From the results of macroscopic extrusion formability, both deformation map and processing map present good criteria to determine optimal forming conditions.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.309-312
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• 2007

Deformation behavior of $Zr_{55}Cu_{30}Al_{10}Ni_5$(at. %) bulk metallic glass(BMG) fabricated by suction casting method has been investigated at elevated temperatures in this study. The BMG was first verified to have an amorphous structure with the analysis of X-ray diffraction(XRD) and differential scanning calorimetry(DSC) data. A series of compression tests has consequently been performed in the region of supercooled liquid temperature to investigate the behavior of high temperature deformation. A transition from Newtonian to non-Newtonian flow appeared to take place depending upon both the strain rate and test temperature. A processing map based on a dynamic materials model has been constructed to estimate a feasible forming condition for this BMG alloy.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.167-170
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• 1997

Magnetostrictions of metallic glass ribbons were measured by fiber-optic Mach-Zehnder interferometry. The saturation magnetostrictions measured here are accurate to within 10%. For accurate measurements the fibers in the ribbons were uncoated, the ribbons were flattened before bonding, and two passes of fiber in the sensing arm were bonded to a single layer metallic glass ribbon at the ends only. Various factors affecting the accuracy of the measurements were also discussed.

• Journal of Magnetics
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• v.4 no.3
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• pp.84-87
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• 1999

It is shown that progressive crystallization of non-magnetostrictive Co-based metallic glass (VITROVAC 6030) leads to an increase of coercivity by more than three orders of magnitude. The mechani는 responsible for this phenomenon are interpreted showing that the main source for the giant increase of the coercivity is the pinning effect on the domain walls originating from the created crystallites of the size much smaller than the domain width (correlation length for ferromagnetic exchange interactions). It is also shown that gradually devitrified non-magnetostrictive metallic glass is an excellent model material for verification of N el's theory describing the Rayleigh rule.

• Journal of Powder Materials
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• v.22 no.4
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• pp.229-233
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• 2015

Porous metallic glass compact (PMGC) are developed by electro-discharge sintering (EDS) process of gas atomized $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ metallic glass powder under of 0.2 kJ generated by a $450{\mu}F$ capacitor being charged to 0.94 kV. Functional iron-oxides are formed and growth on the surface of PMGCs via hydrothermal synthesis. It is carried out at $150^{\circ}C$ for 48hr with distilled water of 100 mL containing Fe ions of 0.18 g/L. Consequently, two types of iron oxides with different morphology which are disc-shaped $Fe_2O_3$ and needle-shaped $Fe_3O_4$ are successfully formed on the surface of the PMGCs. This finding suggests that PMGC witih hydrothermal technique can be attractive for the practical technology as a new area of structural and functional materials. And they provide a promising road map for using the metallic glasses as a potential functional application.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.589-592
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• 2005

Micro-forming is a suited technology to manufacture very small metallic parts(several $mm{\sim}{\mu}m$). Micro-forming of $Zr_{62}Cu_{17}Ni_{13}Al_8$ bulk metallic glass(BMG) as a candidate material for this developing process are feasible at a relatively low stress in the supercooled liquid state without any crystallization during hot deformation. In this study, micro-formability of a representative bulk metallic glass, $Zr_{62}Cu_{17}Ni_{13}Al_8$, was investigated for micro-forging of U-shape pattern. Micro-formability was estimated by comparing $R_f$ values $(=A_f/A_g)$, where Ag is cross-sectional area of U groove, and $A_f$ the filled area by material. Microforging process was simulated and analyzed by applying finite element method. FEM simulation results should reasonable agreement with the experimental results when the material properties and simulation conditions such as top die speed, remeshing criteria and boundary conditions tightly controlled. The micro-formability of $Zr_{62}Cu_{17}Ni_{13}Al_8$ was increased with increasing load and time in the temperature range of the supercooled liquid state. Also, FEM Simulation using DEFORM was confirmed to be applicable for the micro-forming process simulation.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.72-76
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• 1996

The magnetostrictive characteristics of three different forms of magnetostrictive transducers made of 2605SC and 2826MB metallic glasses were measured. In both cases, the two-end-point bonding configuration exhibited the best characteristics. With the two-end-point bonding we measured the effective magnetostrictive coefficient $C_{eff}$ of $1.2{\times}^{-5}Oe^{-2}$, the saturation magnetostriction ${\lambda}_s$ of $7.4{\times}10^{-4}$ and the minimum detectable magnetic field $H_{min}$ of $1.6{\times}10^{-7}Oe$/ √Hz for the 2605SC metallic glass ribbon. Also for the 2826MB metallic glass ribbon, Ceff and ${\lambda}_s$ were $7.6{\times}10^{-6}Oe^{-2}$ and $3.4{\times}10^{-4}$ respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.272-276
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• 2001

Multicomponent $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ bulk matallic glass alloy shows good bulk glass forming ability due to its high resistance to crystallization in the undercooled liquid state.1) In this study, DSC and X-ray diffractometry have been performed to confirm the amorphous structure of the master $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy. To investigate the mechanical properties and deformation behaviors of the bulk metallic $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy, a series of compression tests has been carried out at the temperatures ranging from $351^{\circ}C$ to $461^{\circ}C$ and at the various initial strain rates from $2{\times}10^{-4}s^{-1}\;to\;2{\times}10^{-2}s^{-1}$. There are two types of nominal stress-strain curves. The one shows linear stress-strain relationship meaning fracture at maximum stress, the other shows plastic deformation including steady-state flow. Also DSC analysis for the compressed specimens has been performed to investigate the change of thermal stability and crystallization behavior for the various test conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.2
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• pp.131-136
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• 2000

We have investigated the slurry induced metallic contaminations of undoped and doped silicate oxides surface on CMP cleaning process. The metallic contaminations by CMP slurry were evaluated in four different oxide films, such as plasma enhanced tetra-ethyl-orthyo-silicate glass(PE-TEOS), O3 boro-phos-pho-silicate glass(O3-BPSG), PE-BPSG, and phospho-silicate glass(PSG). All films were polished with KOH-based slurry prior to entering the post-CMP cleaner. The Total X-Ray fluorescence(TXRF) measurements showed that all oxide surfaces are heavily contaminated by potassium and calcium during polishing which is due to a CMP slurry. The polished O3-BPSG films presented higher potassium and calcium contaminations compared to PE-TEOS because of a mobile ions gettering ability of phosphorus. For PSG oxides, the slurry induced mobile ion contamination increased with an increase of phosphorus contents. In addition, the polishing removal rate of PSG oxides had a linear relationship as a function of phosphorus contents.

• Applied Microscopy
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• v.45 no.2
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• pp.37-43
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• 2015

In present work, work-hardening behavior of TiCu-based bulk metallic glass composite with B2 particles has been studied by systemic structural and mechanical investigations. After yield, pronounced work-hardening of the alloy was clearly exhibited, which was mainly related to the martensitic transformation as well as the deformation twinning in B2 particles during deformation. At the early plastic deformation stage (work-hardening stage), the stress-induced martensitic transformation from B2 phase to B19' phase and deformation-induced twinning of B19' phase was preferentially occurred in the around interface areas between B2 phase and amorphous matrix by stress concentration. The higher hardness value was observed in vicinity of interface within the B2 particles which are probably connected with martensitic transformation and deformation twinning. This reveals that the work-hardening phenomenon of this bulk metallic glass composite is a result of the hardening of B2 particles embedded in amorphous matrix.